Selection of lactobacillus strains for urogenital probiotic applications.

Almost 20 years ago, it was shown that lactobacilli expressed properties that appeared to play a role in protecting the host from urogenital infection [1]. Since then, studies have shown that exogenously applied lactobacilli or indigenous lactobacilli, can reduce the risk of urinary tract infection (UTI) [2–4]. The investigations have focused upon the large clinical problem of lactobacilli depletion being associated with UTI, bacterial vaginosis (BV), and yeast vaginitis, which together cause an estimated one billion episodes of disease among women each year. The application of exogenous organisms, such as lactobacilli, to the host is termed probiotics, which is broadly defined as a living microorganism administered to promote the health of the host by treating or preventing disease. While many so-called probiotic products are available, the content and viability of most are unreliable [5, 6], leading to use of strains that do not colonize and therefore do not protect against recurrent UTI [7]. For probiotic applications to the urogenital tract to be successful, it is critical that a scientific basis be established for selection of strains. This should at least shed some light upon their mechanism of action in vivo. Several properties appear to be critical, namely the ability to colonize the host, to inhibit pathogen binding and growth, and to create a balanced flora that resists spermicidal killing [8–10].